The present invention further relates to a method for the accelerated starting of an internal combustion engine, comprising a method of estimating the angular position of a crankshaft of a 4-stroke internal combustion engine prior to synchronization of the engine.
In order to start an internal combustion engine it is necessary to know the position of the crankshaft in order to be able to time the injection of fuel and control ignition within the engine cycle at precisely instants intended by the engine control unit. This knowledge by the engine control unit of the position of the crankshaft is referred to as synchronization. A key problem caused by this synchronization phase is that its completion always requires at least one reference tooth of the target of the crankshaft, which generally has one of these for one revolution of the crankshaft, to be “seen” to go past. What happens is that there cannot be synchronization unless the sensor that monitors the crankshaft target sees this reference tooth go past its beam, which reference tooth, considered in isolation, indicates the position of the crankshaft within the engine cycle to within 360° when the crankshaft has one reference tooth for one revolution of the target which corresponds to one revolution of the crankshaft. Synchronization may, where appropriate, also require one or more fronts of a target associated with a camshaft to be “seen” to go past in order to accelerate this phase which consists in determining the position of the crankshaft, through a combination of the events of the crankshaft target and the events recorded on a camshaft target which, for its part, makes one revolution for every two revolutions of the crankshaft target.
However, even though the position of the ignition point needs to be precise, time can be saved in the starting of the engine if injection is performed earlier than synchronization, more particularly in indirect injection engines where injection is into the inlet manifold, in which engines injection really does take place earlier than ignition for a given cylinder. By way of example, for an indirect injection engine injecting into the inlet manifold, it is necessary to have 360 degrees crank of difference between injection and ignition, which means that, if injection waits until the synchronization phase has been completed, a further 360° are needed before ignition can take place, which implies at least one additional full revolution of the crankshaft before the starting of the engine can be begun, this representing around a further 300 milliseconds.
An overall pre-injection method that offers the possibility of injecting into all of the cylinders on startup before the position of the crankshaft has been determined is known, but such a method has the disadvantage of emitting more pollutants.